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(No Model.) 2 Sheets-Sheet 1,

' A. C. ROBBINS.

TELEGRAPHIO CIRCUIT.

No. 433,421. Patented July 29, 1890.

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No. 433,421. Patented July 29, I890.

INVENTOR UNITED STATES PATENT ()FFICE.

ARTHUR c. ROBBINS, or BROOKLYN, ASSIGNOR TO WILLIAM snnnnnws, on NEWYORK, N. Y.

TELEGRAPHIC CIRCUIT.

SPECIFICATION forming part of Letters Patent No. 433,421, dated July 29,1890.

Application filed April 6 1887. Serial No. 233,935. (No model.)

To all whom, it may concern:

Be it known that I, ARTHUR C. ROBBINS, a citizen of the United States,and a resident of Brooklyn, in the county of Kings and State of NewYork, have invented certain new and useful Improvements in ElectricalCircuits, of which the following is a specification.

My invention relates to improvements in telegraphic or any electricsignal circuits 10 where there are more than two stations, and it isespecially adapted to burglar, police, and fire-alarm telegraph andsignal systems; and the objects of my improvements are, first, toprovide a circuit having way-stations that x 5 shall be always complete,and, second, to furnish such circuit with an automatic grounding deviceby means of which when a break occurs on the line the circuit isautomatically grounded and closed on the faulty side of the neareststation to the break without interfering with the transmitting orreceiving instruments at said station. I attain these objects by theapparatus and the connections illustrated in the accompanying drawings,which are made a part of this specification, and in Which- Figure 1represents two common electroinagnets having soft-iron armatures,grounding-post, resistance coil, and wire connec- 3o tions; Fig. 2, thesame with polarized armatures in the electromagnetic fields. Fig. 3represents common electromagnets having soft-iron plunger-armatures andthe wires as connected. One helix is here shown in section. Fig. i is aplan of an electric circuit,

showing two central stations with their instruments, batteries, grounds,and wires, and three way-stations with my grounding apparatus andshunting-circuit. Fig. 5 shows a 40 part of the resistance-coils inrheostatN or N.

Fig. 6 gives a detail View of galvanometer J or J.

Similarletters refer to similar parts throughout the several views.

With a perfect wire a circuit would be formed from the ground at E, Fig.4, through the batteryB, then through the central station H, relay R,galvanometer J, rheostat N, line L, magnet M, thence through the line 0,re-

. 5o sistance XV, line P, magnet in, and line L to the next station, andin the same manner through stations 2 and 3, through the instruare usedfor registering signals.

ments of home-station H-viz., rheostat N, galvanometer J, and relay Rtobattery B, and thence to the ground at E Thus it is seen that thiscircuit would be a closed circu t, and the magnets M m in station 1 andM m in station 2 and the corresponding magnets in all the other stationswould be magnetized sufficiently, notwithstanding the resistance-coilsWV, W, &c., to hold their armatures A, a, A, a, 850., against themagnets and away from the grounded posts G, G (to. If the line were notbroken at 00, a current of normal strength starting at earth E wouldflow from battery B through relay R, galvanometer J, and rheostat N,through line L to station 1, through the magnet M, line 0, the fixedresistance W, magnet on, and similarly through stations 2, 3, and H,through bat- 7o tery B, to earth at E This current is of sufficientstrength to magnetize the electromagnets, as M m, at all the stationsand hold the armatures, as A a, away from the adjustable points attachedto the ground-plates G, G &c.; but it is of insuiiicient strength toattract the armatures of the receiving-instruments R, R, &c., and causea signal.

Now, if a break occurs in the circuit-as at 00, for instancethearmatures will for an instant be thrown off all the relays; but acomplete circuit being immediately formed between E and E the current inthis circuit magnetizes all the way-station magnets therein, except an,sufficiently to attract their armatures and lift them oif the groundedposts. A second circuit is alsoformed from E to E Thus two circuits areformed, one from E to E including the home-station H and the waystations1 and-2, and the other from E to E containing the waystation 3 andhome-station H. The currentin these circuits is sufficient to excite theelectro-magnets of the grounding apparatus at stations 1, 2, and 3, butinsufficient to attract the armatures of 9 5 the relays R and R at thehome-stations that The resistances G, C, and 0 inserted in thegroundwires of my automatic grounding apparatus, are for the purpose ofequalizing resistances I00 and compelling part of the current to fiowthrough the magnet, thus attracting its armature, and therebyautomatically removing the ground after an opening has been repaired.

They also serve, when in use, to more nearly equalize the normalresistance of the line, as they represent electrically the missingelectromagnets, as m and M after the break shown at m, Fig. l, hasoccurred. \Vhen a break in the circuit does occur, asjust described, ata:, all the armatures go to the earth-points; but the divided circuitthrough D, (Z, D, d, &c., is of nearly equal proportions through themagnets and through the armatures, the resistances at C C, &c.,being ofany required amount. The

-current is of sufficient power through the magnets to attract thearmatures from the ground-points of all except the right-hand magnet ofstation 2 and the left-hand magnet of station 3, which magnets arepractically dead until the break has been repaired. There can be noVibration of the armatures, for when once an armature has been attractedto a magnet there is no possible inducement or chance for it to returnto the groundingpost as long as a current is kept on the circuit-that isto say, when a break occurs, as at 00, a temporary demagnetization ofmagnets M m M m and M m takes place and the armatures are all retractedand make connection with the ground, as G G, 850. Then this occurs, adivided circuit is set up at D. One part of the current passes throughA, G, and O to E, and the other part through 0 IV P to d, where thecurrent again divides, one part passin through a G O to E, and the otherthrough on L M, dividing at D and going to earth at E The currentpassing through M is sufficient to attract the armature A, therebyremoving its ground connection, after which all of the current passes tod, which division and ground is likewise removed by the magnet mbecoming sufficiently magnetized to attract the armature a. Thus one byone the ground-circuits are all removed except those of the armature aand A at stations 2 and 3, respectively. There being no current throughtheir respective electro-magnets on account of the break at as, they areforced to remain against the earth-connections, completing a circuiteach way from the break until the same has been repaired, when magnets mand M in their turn will become magnetized and attract their armatures.In order to maintain the normal condition of the circuit from E to E theoperator at H compensates by means of the rheostat N for the resistanceusually offered by the stations 3 and II. As this resistance isapproximately known to him beforehand, he is at once aware of the numberof stations missing from his circuit. The attendant 011 duty at Hlikewise compensates for stations II, 1,

and 2, and is thus informed of the extent of his circuit. Thetransmitting-keys are normally kept open. I show the key K closed in theshunt-circuit of station 3, by which I cut out the resistance 7 andcause relay R to respond. The current used may be decreased or increasedto cause a signal, so long as the minimum current is of sufficientstrength to retain the grounding-armatures against their magnets andaway from the ground-posts. The keys K and K operate in the same manneras K The relays R and R are adjusted so that they are not affected bythe batteries until one of the resistances V, \V, or N is cut out.Should an accidental ground come in at 00, for instance, thegalvanometers J and J at stations II and 1-1, respectively, wouldimmediately indicate the length of the circuit from each station, andthe trouble would thereby be located. The circuit in this case wouldmeasure the same or nearly the same as a break, for, in the case of abreak, the ground-resistances C 0 would take the place of m and M Therheostats N and N having a large range are used to balance the circuitsand keep the galvanometer-needle at any given point.

The stations, as shown, may be arranged with ordinary telegraphicinstruments or with automatic signaling apparatus, as for police, fire,burglar, marine, or other electric signal-stations. In circuits wherethere is considerable resistance, either because of numerous stations,long lines, or from any other cause, I use the polarized relay made asshown in Fig. 2, the positive pole of which is here represented by theletters 19 p, and the negative-pole by the letters a p, and when economyof room is required I substitute the plunger-magnets shown in Fig. 3.

In a circuit of this character a person at the central station canimmediately detect the location of any key that may have been closed byaccident or design. For this purpose the amount of resistance at NY IV,&c., differs sufficiently, so that if K or K, or any other key, isclosed I can by compensating locate the key closed by the amount ofresistance added. The variance must not, however, be

sufficient to affect the working of the receiving-instruments Thiscircuit would therefore be highly desirable for important worksuch as onrailway telegraph-lines; but in such cases I would prefer to disconnectthe wires from the grounds at E and E and use a metallic circuit, asshown by dotted line in Fig. 4, instead thereof. The batteries B and Bwould in this case be intermediate batteries, and a complete circuitwould be formed from earth at E through C, battery B, the dotted line,battery B, to earth at E permitting full communication between the ter--minal stations and all the stations on the circuit. Of course in thiscase, as soon as the break atsc is repaired there will be no ground inthe circuit. A perfect telegraphic service would thus be assured. lVitha grounded circuit and apparatus any ground or break would immediatelyaffect the galvanometer at the home-station, and by suitableattachments, the galvanometer-needle being provided with the electrode Tand the dial with correspondent electrodes, as at S, the time of suchbreak could be taken, the proper records made, and the break exactlylocated by com pensating for itthat is, by changing the resistance inrheostats N and N until the needle of galvanometers .I and J return tozero I can tell what resistance is missing. By means of this system thefailure of operators to close their keys or to place the line to earth,in order that they may be communicated with when an interruption occurs,which renders ordinary circuits useless, will have no such effect here,and will enable train-dispatchers and other railway oflicials to commandthe movement of trains.

I-Iavin g thus described the action and benefit of my grounding devicein different circuits, that which I claim as new, and desire to secureby Letters Patent, is-

1. In an electric circuit having a current at all times, and where anincreased or decreased currentis used for signaling, the combination oftwo automatic grounding devices at each station, each device arranged toact independently of the other, and each device consisting of anelectro-magnet, an armature controlled by said magnet and arranged topress against a grounded stop when no current is passing through themagnet, and a resistance-coil arranged to connect said grounded stopwith the earth, all substantially as set forth.

2. In an electrical circuit having a current at all times, and where anincreased or decreased current is used for signaling, two automaticgrounding devices at each station, each device arranged to actindependently of the other, and each device consisting of anelectro-magnet, an armature controlled vby said magnet and arranged topress against a grounding-stop when no current is passing through themagnet, and a resistance-coil arranged to connect the grounding-stopwith the earth, in combination with signaling-instruments placed betweensaid grounding devices, substantially as set forth.

Signed at New York, in the county of New York and State of New York,this 24th day of March, 1887.

ARTHUR O. ROBBINS.

Witnesses:

HUG-H COLEMAN, J. B. SABINE.

